Alloy



Z. IEFFRIES AND W. A. GIBSON.

ALLOY.

APPLICATION FILED .IULY 30,1919.

Patented Sept. 7 1920.

`0f from 3% to 4%.

UNITED STATES 'PATENT OFFICE,`

ZAY JEFFRIES AND WILLIAM A. GIBSON, OF CLEVELAND, OHIO, ASSIGrNOItS TOTHE ALUMINUM CASTINGS COMPANY, OF-CLEVELAND, OHIO, A CORPORATION OQHIO.

ALLOY.

Specicatin of Letters Patent.

Patented sept. 7, 192e.

,AppIieation led July 30, 1919. Serial` No. 314,261.

To all whom t may concern Be it known that we, ZAY JEFFRIES and WILLIAMA. GIBSON, citizens ofthe United States, residing at Cleveland, in thecounty of Cuyahoga and State of Ohio, have invented Certain new anduseful Improvements in Alloys, of which the following is aspecification, reference being had therein to the accompanying drawing.

This invention relates to improvements in aluminum alloys and isconcerned especially with aluminum alloys containing zinc, copper andiron.

One object of the invention is to provide anA aluminum v alloycontaining zinq having physical properties, especially tensile strengthand ductility, superior to those ossessed by aluminum-zinc alloys heretoore known.l

. Another object of the invention is to provide an aluminum-zinc alloyhaving superior physical properties in combination with ease ofpreparation and good casting, machining and workingv qualities.

Binary alloys of aluminum and zinc have been extensively investigatedand it has long been known that the elfect of zinc when added toaluminum is to produce rela` tively close grained and non-porouscastings. By many it has been supposed that these aluminum-zinc alloysessentially are subject to excessive corrosion and offer relativelyslight'res'istance to shock. It is now known, however, that theseobjectionable characteristics are entirely obviated when suitable careis taken to insure uniform mixing of the constituent metals in properproportions.

'lhe ternary alloys of aluminum, zinc and copper have been only slightlinvestigated so far as we are aware. heir physical properties, however,so far as known, are a pre'ciablybetter than those of the binary auminum-zinc alloys. We have found that an aluminum alloy containingabout 8% zinc and 3% copper has a tensile strength ranging from 20,000pounds to 26,000 pounds per square inch, and an elongation (Here, aselsewhere in this application, the composition percentage is byweight)..

Ve have discovered that these physical properties can be very greatlyimproved by the addition to a ternary alloy ofthe above composition offrom 0.5% to 1.5% of iron. While the proportions of the variousconstituents may vary through a considerable range and still retain insubstantial measure the advantages of this four part alloy,-

the composition which we prefer to employ is one containing from 6% to8% zinc, from 2.5% to 3.5% copper, from` 1% to 1.5% iron,

v andthe remainder aluminum. Alloys withbetween 55 and 60, and specificgravitiesless than 3.0. By increasing the percentage of zinc anddecreasin that of aluminum greater tensile strengt is obtained but atthe sacrifice of ductility.

An alloy of the preferred composition can be made up in various waysknown to those skilled in the art. One successful method is as follows:

First is prepared a rich'alloy-containing three parts of copper to onepart'of iron together with a sufficient amount of aluminumto reduce` themelting point ofthe alloy to approximately that of aluminum.

The calculated amounts of aluminum and' of the above rich alloy aremelted together and the calculated quantity of zinc is then adder?.While stirring. After thorough stirring the metal is heated to thedesired pouring temperature. This alloy may be cast equally well in sandmolds and permanent molds and by reason of the zinc content, whichrenders the melt quite fluid, it will completely and quickly till themold, even where there are thin sections. The alloy is easy to makebecause no extremely` high tempera-tures are required( Castings of thisalloy are very dense, have good machining qualities and are not ea'silycorroded o1- aifected by shocks.

We have -found that it is not advantageous to heat treat these alloys,for while heat treatment may in some cases increase tensile strengthsomewhat, it results 1n .a relativel greater decrease of the elasticlimit. or most purposes the lowerlng of the elastic limit wouldoutweighl the advantages incident to any increased tensile .amounts ofzinc and 1% added iron.

strength so that, as stated, heat treatment of the alloy is notordinarily advantageous.

The accompanying drawing shows graphbrokelrline curves represent thealloys Without iron and the full linecurves represent.

the alloys with iron. The horizontal scale at the bottom represent theper cent. of zinc, the Vertical scale at the left, tensile strength Iand the vertical scale atv the right, the per cent. elongation. It willbe observed that the addition of 1% iron to the ternary alloy markedlyincreases both the tensile strength and the elongation. With 7% to 8%Zinc the alloy presents a highly advantageous combination of tensilestrengths ranging from over 27,500 pounds to over 28,500 pounds persquare inch and elongation ranging `from over 6% to over 7%, whereas theternary alloy without the iron has a tensile strength ranging well below24,000 pounds per square inch and an elongation ranging well below 4%.

As has already' been indicated, if the use ofthe alloy requires a stillhigher tensile strength this can be obtained at the sacrifice ofductility, by increasing the quantity of zinc above, say 8%, andmaintaining the iron and copper contents. However, these aluminum alloyscontaining more than 8% zinc with 1% .iron and 3% copper are not onlystronger but also more ductile than the aluminum alloys containing zincAand copper alone. For example, as will be noted on reference to thedrawing, with 15% zinc and 3% copper and 1% added iron the tensile vstrength is 37,000 poundsper square inch,

and elongation 2.5% whereas the saine composition without the iron has atensile strength of 32,000 pounds per square inch and an elongation of1.8%.

As 1s well known to those having commercial experience W1th alumlnum, it1s impossible to secure the metal in commercialV quantities free fromimpurities, notably iron and silicon. The iron thus present will, ofcourse, be taken account of in introducing additional iron; and careshould be taken to keep the amount of silicon present as low asYpossible. It may be observed in connection with the vvalues mentionedfor tensile strength and ductility, that in the case of castings madefrom our improved alloy the tensile strengths increase and the ductilitydecreases slightly as the castings age.

In the foregoing description We have indicated the preferred range ofcompositions and the preferred method of preparing our improved alloy,but it isto be understood that our invention is not limited in theserespects except as specified in the appended claims. f

What We'claim is:

1. An alloy 'containing aluminum, copper, zinc and iron, the coppercontent being from 2% to 5%, the zinc content being from 4% to 25%, theiron content being from 0.6% to 1.8%, and the aluminum making up theremainder.

2. An alloy containing aluminum, copper, zinc and iron, the coppercontent being from 2% to 5%, the zinc content being from 4% to 16%,'theiron content being from .6% to 1.8%, and the aluminum making up theremainder.

3. An alloy containing aluminum, copper, r/iinc and iron, the coppercontent being from 2.5% to 3.5%, the zinc content being @om 6% to 8%,the iron content being from 0.8% to 1.5%, and the aluminum making upthel remainder.

4. An alloy of aluminum, copper, zinc and iron containing approximatelyA88.7% aluminum, 3% copper, 1.3% iron and 7% zinc.

5. An alloy containing aluminum, copper, zinc and iron, the coppercontent being approximately 3%, the iron content being approximately1.3% and the Zinc content ranging from 4% to 25%, and the aluminummaking up the remainder.

6. An alloy containing aluminum, from 2% to 5% of copper, from .5%` to1.5% of iron and zinc and having a specific gravity less than 3.0.

In testimony whereof, we hereunto affix cur signatures.

ZAY JEFFRIES. WILLIAM A. GIBSON

